The flow-adjusting valve is an important component of the refrigeration system, and is another one of four fundamental components of the refrigeration system besides the evaporator, the compressor and the condenser. Operation process of the flow-adjusting valve is generally as follows: with the energizing or de-energizing of the coil device, the valve needle is driven to adjust the opening degree of the valve port, so as to adjust the flow of the refrigerant. Furthermore, the flow regulating valve is widely used in other fluid control fields such as the hydraulic system and the oil transportation fields.
In the prior art, a flow regulating valve is disclosed in Chinese patent application No. 200580023202.7. Referring to FIG. 1 and FIG. 2, FIG. 1 is a structural schematic view of a flow regulating valve in the prior art, and FIG. 2 is a partial enlarged view of the flow regulating valve in FIG. 1.
As shown in FIG. 1, a motor 70 is provided in the motor shell 62, and the lower shell 60 of the motor shell 62 is connected in the head portion 48 in a thread cooperation manner. As shown in FIG. 2, the valve unit 40 includes a discharge piston 130 (equivalent to a nut), and the discharge piston 130 has an internal thread and is configured for housing a driving shaft 78 (equivalent to a screw rod) which has an external thread. The discharge piston 130 is extended a longe length in the axial direction, and is slidably mounted in the sleeve 146 which is mounted in the lower shell 60. The discharge piston 130 is limited by the sleeve 146 and cannot rotate circumferentially. When the motor 70 drives the driving shaft 78 having an external thread to rotate via a gear system, since the discharge piston 130 cannot rotate circumferentially, it can only move axially to thereby drive the valve unit 40 to regulate the opening degree of the valve port on the valve seat 22. However, the flow regulating valve in the prior art has the following drawbacks:
Firstly, the valve unit 40 includes a rear component 94 which is connected in a middle component 96 in a thread cooperation manner. Thereby the axial position of the discharge piston 130 is limited. As shown in FIG. 2, since the discharge piston 130 needs to close or open a small valve port 120b, the discharge piston 130 should not wobble in the radial direction. That is, not gap is formed between the discharge piston 130 and the rear component 94 or the middle component 96 in the radial direction. Otherwise the sealing performance in sealing the small valve port 120b will be affected. The machining and assembling of the components and parts of the valve body may cause a large coaxial error, resulting in a large coaxial error between the driving shaft 78 and the discharge piston 130. Since the discharge piston 130 cannot wobble in the radial direction, the driving shaft is likely to get stuck.
Secondly, the rear component 94 is connected with the middle component 96 through threads, as the discharge piston 130 and the valve unit 40 are moved in the axial direction, the thread cooperation may become loosened, resulting in a low reliability in axially limiting the discharge piston 130.
Thirdly, the discharge piston 130 needs to be fixed in the sleeve 146 of the lower shell 60, such that it is circumferentially limited by the sleeve 146 and thus cannot be rotated. In view of this, the length of the portion of the discharge piston 130 that is protruded out of the valve unit 40 should be sufficient such that it can be extended into the sleeve 146. In this structure configuration, the driving shaft 78 cooperated with the discharge piston 130 also has a large length, therefore the driving shaft 78 has a large deflection, and it is difficult to ensure the coaxial degree between the discharge piston 130 and the driving shaft 78 when assembling the same, and if they are not assembled in proper, the resistance moment will be increased, and moreover, the driving shaft 78 will get stuck.
Fourthly, as is described above, it requires that the discharge piston 130 be protruded out of the valve unit 40 at a sufficient length such that it can be extended into the sleeve 146. Accordingly, the driving shaft 78 and the lower shell 60 have large lengths in the axial direction. Thereby the material cost is increased.
In view of this, there is an urgent demand for the person skilled in the art to make an improvement to the flow regulating valve in the prior art, such that, on the one hand, the coaxial error between the screw rod and the nut, resulting from the machining and assembling of the components and parts, can be eliminated, and on the other hand, the axial position of the nut can be limited more reliably.